Various devices and methods have been utilized to conduct blood from the heart to assist with blood circulation in a patient. This is often desirable or necessary in cases where a patient is experiencing congestive heart failure and a transplant organ has either not been located, or the patient is not a suitable candidate for a transplant. The blood pumps are typically attached directly to the left ventricle of the heart, however, at least one blood pump system locates the pump remotely, such as subcutaneously in the manner of a pacemaker. In this regard, see U.S. Pat. No. 6,530,876, the disclosure of which is fully incorporated by reference herein. In this situation or similar situations, a cannula may be used to create an inflow conduit from the heart (an intra-thoracic location) to a pump located in a superficial (non-thoracic cavity) location, which may be the so-called “pacemaker pocket.” The pacemaker pocket is a location usually accessed by a surgical incision generally parallel to and below the collarbone extending down toward the breast, and over the pectoral muscle. Sometimes the pacemaker pocket is made below the muscle. The pump, to which the cannula is connected, is intended to sit in the pacemaker pocket and is preferably at, but not limited to, a location on the right side of the chest.
General cannula implantation methods known and usable in connection with the present invention may involve many different approaches and several of the representative approaches are described further below. For example, the cannula may be implanted by directly invading the thoracic cavity. Surgical methods include so-called open heart surgery in which a median sternotomy is made to fully expose the heart within the thoracic cavity. Still other surgical methods include less invasive surgical methods such as a thoracotomy, mini-thoracotomy, thoracoscopic, or any other less invasive approaches. Any of these or other surgical methods can be used to implant the cannula in fluid communication with any desired location of the heart as described herein.
To accommodate such implantation methods and the chest anatomy of a patient, it is highly desirable for the inflow cannula to be as flexible as possible without kinking. One consideration that limits this design objective, however, is that the cannula must be of a sufficient stiffness during implantation to extend into the desired area of the patient's heart. For example, the cannula might be forced through the left atrial wall of the patient's heart to be placed in fluid communication with the left atrium. The cannula may be inserted through a hole in the atrial wall created by a dilator, the cannula itself, or another device. Therefore, devices or methods for providing the cannula with sufficient stiffness to extend through the wall of a heart without compromising the flexibility of the cannula after implantation would be desirable.